Dry spinning process



June 10, 1958 s, s rr 2,838,364

DRY SPINNING PROCESS I Filed Jan. 7, 1955 2 sham-sheet 1 I 16 FIG. 1

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DRY SPINNING PROCESS Filed Jan. 7, 1955 2 Sheets-Sheet 2 FIG.2.

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. PRIOR ART ARTHUR 5. SMITH INVENTOR.

ATIQORNE'XS U i d States Patent DRY SPINNING PROCESS Arthur S. Smith, Kingsport, Tenn., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application January 7, 1955, Serial No. 480,486

3 Claims. (Cl. 18-54) This invention relates to the preparation of synthetic filaments and fibers of increased luster, stiffness and increased bulk. More particularly this invention relates to improved dry spinning methods and apparatus for producing from cellulose ester spinning solutions hollow filaments and fibers of annular cross-section having such desirable characteristics. The hollow space in the fiber is continuous throughout the length of the fiber. Furthermore, this invention also relates to fabrics and other articles of manufacture made of, or containing such annular cross-section filaments and fibers.

-Heretofore, various processes and apparatus have been provided for the production of synthetic filaments and fibers of various crossrsection. Generally these Wellknown cross-sections fall within one or two classifications such as relatively narrow and rectangular crosssections, or round or round-like cross-sections which include filaments of round and fiat sides, clover-leaf configurations and other related variations produced by physicallydeforming the filament, after it has assumed its normal shape, as it issues from the spinning cabinet.

Typical methods and apparatus for dry spinning solutions into synthetic fibers are disclosed in U. S. Patents 2,000,047 and 2,000,048 of May 7, 1935, to H. G. Stone. These patents describe methods including the forcing of a heated cellulose ester spinning solution-through a spinnerette having a plurality of separated round orifices and into a drying chamber containing an evaporation atmosphere maintained at a suitable drying temperature. By such controlled conditions filaments can be consistently formed of approximately round or clover-leaf crosssection as contrasted to the filaments previously produced of elliptical shape.

Also, as shown in U. S. Patent 1,695,455 of December 18, 1928, by drawing the filaments from the round orifice spinnerette in a direction other than perpendicular to the horizontal face of the spinnerette, filaments having a more or less flattened cross-section are produced. It is also known that slight variations from the round crosssection can be caused by adjusting the particular evaporating conditions under which the filaments are dried in the spinning cabinet. A suitable selection of these conditions will permit the production, from spinnerettes having round orifices, of filaments with either a smooth or an unsymmetrical, irregular surface.

In U. S. Patent 1,773,969 of August 26, 1930, the technique of the extrusion of filament forming solutions through circular orifices into evaporative atmospheres is also discussed. As described therein it is suggested that the outer layer of the stream of cellulosic material which A is initially circular in cross-section as it issues through the spinnerette orifices hardens or solidifies first forming a skin that is tougher and less fluid than the interior. After this initial hardening of the outer surface, the interiorof the filament is precipitated or dried and thereby shrinks while the outer layer is further hardened. The

outer shell of the filament being tougher and more deto collapse and to assume a very irregular cross-section which is in the form of a figure of many indentations of varying sizes and shapes and which is often quite flat.- Because of the irregularity of shape and flatness of the cross-section of such filaments, their covering power, their bulk, stiffness and luster are quite irregular. This Patent 1,773,969 then describes the use of spinnerettes having orifices of compact or squat shape having indentations in the form of re-entrant angles. The re-entrant angles can be constituted by straight or curved boundary lines. However, the filaments produced by extruding cellulose ester filament forming solutions through such orifices have more or less cross-sections characterized by rounded surfaces. 7

As described in Hickey Patent 2,373,892 of April 17, 1945, I-beam type cross-section filaments or fibers having a high degree of resiliency and crush resistance may be produced by extruding a suitable cellulose ester solution through a spinnerette having rectangular orifices. Fibers made from such I-beam filaments are particularly useful for manufacturing carpet materials, as well as for the manufacture of rugging and other pile fabrics. ever, the ends of the Lbeam are of a round shape and do not extend. substantially above the flat section of the I-beam. I An object, therefore, of the present invention is to provide a process for preparing filaments and fibers with an increased bulk and stiffness as compared to above discussed prior art fibers of equivalent denier and chemical composition.

Another object of this invention is to provide a process for preparing hollow filaments and fibers.

approximately 210 degrees. H 7 Another object is to provide staple fibers made from a plurality. of hollow filaments having an annular c rosssection. I

.Again another object is to provide new and novel fabrics containing such annular cross-section filaments or staple fibers.

Still another is to provide a novel filling material of increased resistance to matting which is suitable to employ in' pillows and the like. I

Yet another object of this invention is to provide fibers adaptable for use in manufacturing cigarette filters.

Other objects will appear hereinafter. A In accordance with the present invention, these and other objects may be attained by forcing asuitable spinning solution through a, spinnerette having a plurality of 'filament forming orifices therein in the shape of a sector of a circle which is subtended by an angle of approximately 210 degreesand drying the resulting filaments in a spinning cabinet under carefully controlled conditions of temperature while subjecting the filaments topredefilaments as they leave these orifices temporarily assumea Patented June 10, 1958 How- O-shaped cross-section. However, in accordance with my invention, by careful control of the extrusion rate, the drafting rate and drying temperatures, the arms of this will be brought together forming a hollow filament of annular cross-section. Under preferred ranges of operation, as suggested above, and as described in detail further on in this specification, the annular cross-section will be substantially uniform for each of the simultaneously extruded filaments.

In general the spinnerette having these partially circular orifices may be employed with any suitable spinning cabinet such as, for example, one of the general kind described herein. The annular cross-section filaments, however, can be prepared in accordance with my invention within a satisfactoryrange of spinning, drafting and solution conditions .as is described hereinafter.

The increased bulk of .fibers made of annular crosssection filaments depends on the resistance of the filaments to compressive forces when formed into fibers or yarn.

The present invention will be further understood by reference to the following detailed description in which specific examples of my invention are given and to the related drawings in which:

Figure 1 is a schematic elevational view, partly in section, showing a spinnerette which has filament forming orifices in the shape of a sector of a circle which is subtended by an angle of approximately 210 degrees positioned in a suitable dry spinning cabinet which is equipped with suitable auxiliary apparatus;

Rig. 2 :is a view of the face of a spinnerette showing a plurality of filament forming orifices of such novel shape;

Fig. 3 is a greatly enlarged representation of the spinning solution coming out of the orifices of the spinnerette and forming into the annular cross-section "filaments;

Fig. 4 is a reproduction of an actual photomicrograph showing the annular cross-section of several filaments of the present invention; and

Fig. 5 is a reproduction of an actual photomicrograph showing in cross-section several filaments made by employing a spinnerette having round orifices in accordance with a prior art method.

The similar parts in the several figures are identified by the same numerals.

Referring to Figure 1, there is shown schematically a side elevation view, partly in section, of a spinning cabient 11 and its associated apparatus by which the novel hollow filaments and fibers of the instant inven- ,tion may be manufactured. Mounted at the top of the cabinet is a candle filter unit .12 to which is connected a spinnerette 13 which in accordance with this invention has a plurality of orifices 14 therein which are of shape shown in Fig. 2. The .face of this novel type of spinnerette with the orifices 14 therein is shown in the greatly enlarged view of Fig. 2. The candle filter may be uniformly heated by means of heating coils, not shown, which are positioned so as to surround candle filter 12, and through which coils may be circulated any appropriate heat exchange medium such as water maintained at the desired temperature.

Spinning solution of composition described hereinafter is supplied from conduit 16 through valve 17 to pump 18 which forces the solution at the desired rate to the candle filter unit 12, thence to spinnerette 13 from which it is initially extruded through the orifices 14 in the form of filaments having a C-shaped cross-section.

The filaments 25 pass downwardly in the cabinet 11 while progressively losing solvent by evaporation until, in a substantially solidified and dried condition they leave the cabinet 11 and pass around godet roll 20, which is positioned below the lower end of the spinning cabinet 11. Godet roll 20 is driven at a uniform speed by means, not shown, to give the desired draft to the filaments 25. From godet roll Ztlthe filaments pass over the usual guide rolls '21 and are finally wound onto a bobbin 22 4. after an appropriate twist has been imparted thereto, by means not shown.

To facilitate drying of solvent from the filaments during their travel through the cabinet, heated air is supplied to the cabinet 11 by means of inlet conduits 23 and 24 positioned respectively adjacent the lower and upper ends thereof, the air passing through the cabinet and emerging through outlet conduit 26 positioned at a substantial distance below spinnerette 13, as illustrated.

The change of the cross-section of the filaments while in the cabinet from an initial C-shaped cross-section shape to the desired annular cross-section shape is schematically illustrated in Figure 3. As shown at 25, the filaments have just been formed by the 210 degree sector orifices and are substantially of a C-shaped cross-section. Further on, in the downward progress of the filaments under the controlled condition of drafting and drying, the arms of the C have been drawn together to form the desired annular cross-section filaments 25A which are depicted greatly magnified in Figure 4.

My process is described in further detail in the following examples.

EXAMPLE 1 A spinning solution consisting of 29.5 cellulose acetate, 1.5% water and the remainder being the solvent, acetone was spun into annular shaped cross-section filaments of denier using the apparatus and its general operation as described above in connection with Fig. 1. The spinnerette had 19 orifices therein. The specific conditions of operation are shown in Table I, column 1.

EXAMPLE 2 A spinning solution consisting of 29.5% cellulose acetate, 1.5% water and the remainderbeing acetone solvent was spun into annular shaped cross-section filaments of denier using the apparatus and its general operation as described above in connection with Fig. 1. The spinnerette had 7 orifices therein. The specific conditions of operation are shown in Table 1, column 2.

EXAMPLE 3 The same spinningsolution was ,spunin the .sa e .SPin- .ning cabinet through a spinerette having round orifices with the conditions of operation like that in column 1. The results are shown in column 3 of Table I and clearly show that the ,annularfilaments are superior in bulk and stiffness over the thus formed regular cross-section filaments.

Table I Annular Annular Regular Filaments filaments Filaments Damien." Filaments 'D/F Hole Shape Diameter oi'Sector, mm. 0066 Draft 1 Spinning Speed, Meters/Min- O. F. Water Temperature- O" Top Inlet Air TemperatureC Bottom Inlet Air Temperature-O.

Top Air Input, Cubic Feet/ Minute.

Bottom Air Input, CunieFect/ Minute.

Luster Dry strength,g./d

Wet Strength, g./d.

Dry Stretch, Percent- Wet Stretch, Percent Bulk Factor Specific Volume, Cubic In.

In this table ,the air flow in cubic feet per i ninl te is calculatedfor onehundredspinning cabinets. The extrusion speed in meters vperminute represents the rate at which the spinning solution is forced out of the spinnerette. This, in cooperation with the draft rate enables thefilaments to change from the'initial cross-sectionto the cross-section while drying. For sharply defined hollow filaments, a spinning draft of above 0.6 should be employed. Preferably the draft is approximately 1.2 and a draft of 1 or above gives superior results.

Draft may be defined rather broadly as the'ratio of the linear velocity of wind-up of the filaments to the linear velocity of extrusion of the spinning solution. More specifically, draft may be defined as the ratio of the linear velocity at which the filaments are wound onto and off the godet roll of a dry spinning cabinet to the calculated average linear velocity at which the quantity of spinning solution necessary to the formation of any one of the plurality of filaments comprising the bundle of filaments wound onto and off the godet roll is extruded through any one of the plurality of orifices in the spinnerette employed in the spinning operation, the velocities being expressed in the same units of distance per unit time. For example, if the filaments are wound up at the godet roll at the same linear velocity that the spinning solution is extruded from the spinnerette, the draft is 1.0, thus signifying that the linear speed of wind-up is 100% of the extrusion speed. Similarly, if the filaments are wound up or withdrawn from the cabinet at the godet roll at a linear speed 50% greater than the speed of extrusion, the draft is 1.5, and so on.

Other items of Table I'are more or less self explanatory when considered in connection with Figure 1 of the drawings or the related description.

The temperatures listed in Table I are temperatures used to produce a quality product with a particular cellulose ester-acetone solution. These temperatures are somewhat critical and may vary over a substantial range. Changes in cellulose esters and cellulose ester to acetone ratios may require some alterations or changes in these temperatures.

While particular emphasis has been made to preparing annular shaped cross-section filaments from cellulose acetate, my process will also operate satisfactorily with the single and mixed organic acid esters such as those containing 2 to 4 carbon atoms.

I have also found that my spinning process employing spinnerettes having the novel orifices of the present invention operates very well over a range of deniers per filament of 1.5 to 43, although higher denier filaments can be satisfactorily made by my invention.

That the bulk of the annular-shaped cross-section fiber, because of its particular cross-sectional shape and increased surface area, is greater than the clover-leaf or regular cross-section fiber of equivalent denier is also shown in Table I, where comparisons of equivalent samples of regular and annular-shaped cross-section yarn made from the same spinning compositions are set forth.

The bulk data in Table I are determined by a test which has been developed in which yarn is wound under a specified tension until it fills a spool of a known volume. The amount of yarn required to fill this volume is weighed. From this weight the Bulk Factor and Specific Volume are calculated. The Bulk Factor is calculatedby the following formula:

(Volume of SpoolXDensity of Fbers-eWeight of Yarn to fill spool) 100=Bulk Factor This formula expresses the bulk as a percentage ratio of I the space occupied by the yarn to the space which would refiected'offthese panels to the photo-electric cell imparts a potential which is translated into a numerical luster level. On comparative tests the clover-leaf panel of filaments record 0.77 volt whereas the annular cross-section filaments of the same denier record 0.88 volts.

EXAMPLE 4 Cigarette filters were prepared fromannular shaped cross-section cellulose acetate fibers. Their interesting bulk and stiffness properties permit the construction of filters of interesting design. The hollow cross-section also permits filling the fibers with other filtering compounds.

Yarn composed of annular shaped cross-section filaments is somewhat stiffer and more resilient than yarn having regular or clover-leaf cross-sections. The effect on stifiness of cross-sectional shape can be estimated by comparing movements of inertia of fibers having different shapes but the same cross-sectional area. By this method it was determined that annular-section filaments are substantially stiffer than normal filaments of equal size.

The inherent properties of cellulose acetate fibers of annular-shaped cross-section are such that they offer numerous desirable properties in both woven and knitted fabrics. In such fabrics as ninons, marquisettes, and voiles, the annular-shaped section fibers produce fabrics having desirable crispness and stiffness which are usually obtained only by special processing techniques or by special finishing. In fiat fabrics, such as talfetas, twills, and satins, the increased bulk of the annular shaped fibers produce fabrics having greater cover and thickness for a given weight of material. On the other hand there is the possibility of using less material to produce fabrics of the same cover and thickness thereby decreasing the cost. Yarns having an annular cross-section produce fabrics with less tendency for the yarns to slip resulting in higher seam strength. This characteristic is particularly important in certain fabrics, for example, satins and twills. Loom finished tafietas have a crisper feel when made from section yarns.

Knitted fabrics from yarns with annular-shaped sections exhibit increased body and hand which make them more desirable for certain uses such as sport shirts, mens ties, and dress goods. Yarns spun from staple fibers of cross-section exhibit increase in bulk and stiffness as do the filament yarns. In addition, fabrics from these yarns have a wool-like feel or hand. In all of the fabrics which have been produced from cellulose acetate fibers of the annular-shaped cross-section fabric properties have been obtained which are desirable and which are not obtained in cellulose acetate fibers of regular cross-section.

I claim:

1. The method of forming cellulose organic acid ester filaments having a relatively high bulk and of a closed C-shaped cross-section, which comprises extruding a cellulose organic acid ester filament forming solution through a spinnerette equipped with extrusion orifices in the form of a sector of a circle the arcuate boundary of which is subtended by an angle of 210 degrees, and into a dry spinning cabinet, drafting the thus formed C-shaped cross-section filaments while drying the filaments at a temperature within the range of to C. whereby the cross-section of the filaments is changed to said closed C-shaped cross-section.

2. The method of forming cellulose acetate filaments having a relatively high bulk and of a closed O-shaped cross-section which comprises extruding a cellulose acetate filament forming solution through a spinnerette equipped with extrusion orifices in the form of a sector of a circle the arcuate boundary of which is subtended by an angle of 210 degrees and into adry spinning cabinet, drafting the thus formed C-shaped cross-section filaments at a draft ratio within the range of approximately 1 to 1.2 while drying the filaments at a temperature within the range of 60 to 90 C. whereby the crosssection of the filaments is changed to said closed C-shaped cross-section.

3. The method of forming cellulose acetatefilaments having a relatively high bulk and of a closed C-shaped cross-section which comprises extruding a cellulose acetate filament forming solution through a spinnerette equipped with extrusion orifices in the form of a sector of a ,circle .the arcuate boundary of which is subtended by an ang'leof 210 degrees and into adry spinning cabinet, drafting the thus formed G-shaped cross-section "8 filaments at a draft ratio of 1.2 while drying the filaments within the range of 60 to 90 C. whereby the crosssection of the filaments is changed to saidrclosed G-shaped cross-section.

References Cited in the file of this patent UNITED STATES PATENTS 2,000,048 Stone May 7, 1935 2,013,688 Kinsella Sept. 10, 1935 2,026,730 Dreyfus Jan. 7, 1936 2,313,296 Lamesch Mar. 9, 1943 2,373,892 Hickey Apr. 17, 1945 2,403,437 Kohorn July 9, 1946 2,434,533 Wurtzburger Jan. 13, 1948 2,588,583 Small .et a1 Mar. 11, 1952 2,588,584 Small Mar. 11, 1952 2,673,368 Denyes Mar. 30, 1954 2,677,184 Webb May 4, 1954 

1. THE METHOD OF FORMING CELLULOSE ORGANIC ACID ESTER FILAMENTS HAVING A RELATIVELY HIGH BULK AND OF A CLOSED C-SHAPED CROSS-SECTION, WHICH COMPRISES EXTRUDING A CELLULOSE ORGANIC ACID ESTER FILAMENT FORMING SOLUTION THROUGH A SPINNERETTE EQUIPPED WITH EXTRUSION ORIFICES IN THE FORM OF A SECTOR OF A CIRCLE THE ARCUATE BOUNDARY OF WHICH IS SUBTENDED BY AN ANGLE OF 210 DEGREES, AND INTO A DRY SPINNING CABINET, DRAFTING THE THUS FORMED C-SHAPED CROSS-SECTION FILAMENTS WHILE DRYING THE FILAMENTS AT A TEMPERATURE WITHIN THE RANGE OF 80 TO 90*C. WHEREBY THE CROSS-SECTION OF THE FILAMENTS IS CHANGED TO SAID CLOSED C-SHAPED CROSS-SECTION. 